High temperature silicone based subsea insulation

ABSTRACT

The invention is an insulation material which comprises a silicon based matrix and a plurality of non-metallic beads supported in the matrix. In one embodiment of the invention, the matrix comprises a platinum cured, addition cured silicon material and the beads comprise a mean diameter of less than about 60 microns and an isostatic strength of at least about 10,000 psi. The insulation material may be used in conjunction with subsea oil and gas production equipment, such as pipelines, wellheads and christmas trees.

This application is based on U.S. Provisional Patent Application No.60/302,926, which was filed on Jul. 3, 2001.

BACKGROUND OF THE INVENTION

The present invention is related to an insulation material for use onsubsea oil and gas production equipment.

When subsea oil and gas wells are located at depths of 5,000 feet ormore, the pipelines and wellhead equipment are exposed to seawater whichis just a few degrees above freezing. This same temperature can exist inshallow water at extreme latitudes, such as in the North Sea. During atemporary well shutdown, hot produced fluids within the productionequipment become stagnant and are cooled by the surrounding seawater. Ifthe stagnant fluids approach the seawater temperature, hydrates can formin the equipment and block the flow of the fluid.

Thermal insulation is sometimes installed around subsea pipelines andwellhead equipment to slow the cooling process and delay hydrateformation until flow can be restored. To perform successfully in thisenvironment, a thermal insulation material must have a low thermalconductivity, exhibit acceptable mechanical properties such asflexibility and impact resistance, and be economical to install.

In many subsea wells, especially those in deep water, the insulationrequirements are further complicated by the extreme temperatures of thehydrocarbon fluids exiting the well. In some cases the temperature ofthe exiting fluids may reach 300° F. or higher, and the fluids willconsequently heat both the surrounding equipment and the insulation.Therefore, any insulation material which is used on such wells must beable to withstand these extreme temperatures without detriment to itsthermal or mechanical properties.

Although insulation materials exist which can withstand these relativelyhigh temperatures, they are inherently brittle. Therefore, thesematerials are unable to meet the flexibility and impact resistancerequirements of many applications. Examples of these types of prior artinsulation materials include syntactic phenolic foams and hightemperature epoxy resins. Furthermore, because of their brittle natureand exothermic curing properties, these materials are difficult andexpensive to install and repair.

Conversely, existing insulation materials which exhibit acceptableflexibility and impact resistance characteristics are unable towithstand the relatively high flow temperatures present in may deepwater wells. Examples of these types of prior art materials includeamine cured epoxies, urethanes, and polypropylenes.

SUMMARY OF THE INVENTION

In accordance with the present invention, these and other disadvantagesin the prior art are overcome by providing a thermal insulation materialwhich comprises a silicone matrix and a plurality of non-metallic beadswhich are supported in the matrix. In one embodiment of the invention,the matrix comprises Silastic® E RTV silicone rubber, which is aplatinum cured, addition cured silicone material. In addition, thenon-metallic beads comprise hollow glass beads which have a meandiameter of less than about 60 microns and an isostatic strength of atleast about 10,000 psi.

The thermal insulation material of the present invention exhibits manyadvantageous properties which make it particularly suitable for use onsubsea oil and gas production equipment. The matrix material is highlyflexible, which makes the insulation material resistant to crackingunder thermal and mechanical stresses. In addition, since the matrixmaterial produces no by-products or exothermic effects during curing,the insulation material can be cast-in-place in thick sections.Furthermore, due to its relatively low thermal conductivity, theinsulation material is an excellent insulator. Moreover, the insulationmaterial can withstand extreme temperatures in excess of 300° F. withoutdetriment to its thermal or mechanical properties.

These and other objects and advantages of the present invention will bemade apparent from the following detailed description, with reference tothe accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross sectional view of the thermal insulation material ofthe present invention; and

FIG. 2 is a cross sectional view of an exemplary subsea christmas treehaving the thermal insulation material of the present invention appliedthereto.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention is an insulation material which is suitable forsubsea oil and gas production equipment. Referring to FIG. 1, theinsulation material, which is indicated generally by reference number10, comprises a matrix 12 and a plurality of micro beads 14 which aresupported in the matrix. The matrix 12 ideally comprises a suitablesilicone material. More preferably, the matrix 12 comprises an additioncured silicone material. In accordance with one embodiment of thepresent invention, the matrix 12 comprises a platinum cured, additioncured silicone material, such as the Silastic® E RTV silicone rubberproduct which is available from Dow Corning Corporation.

In the context of the present invention, addition cured silicones arepreferred over condensation cured silicones because they produce nobyproducts or exothermic effects during curing and are therefore moresuitable for casting in thick sections. In contrast, condensation curedsilicones require moisture from the air in order to cure properly andproduce byproducts during curing, making them unsuitable for casting inthick sections. However, the matrix 12 could comprise any suitablesilicone material, including any other addition cured silicone material.Moreover, the matrix 12 could comprise a condensation cured siliconematerial if the material is cast in relatively thin sections.

The addition of the micro beads 14 to the matrix 12 reduces the densityand the thermal conductivity of the insulation material 10. The microbeads 14 are preferably hollow, preferably glass beads having a meandiameter of up to about 60 microns. In order to withstand thehydrostatic pressure of a deep sea environment, the beads preferablyhave an isostatic strength of at least approximately 10,000 psi.Suitable micro beads for use in the present invention includeScotchlite™ H50/10,000 EPX Floated Series Glass Bubbles, which areavailable from 3M Corporation. These micro beads comprise an epoxysilane surface treatment which helps the beads adhere to the siliconematrix 12. While glass micro beads 14 are preferred, the micro beadscould be made of any suitable material, such as a ceramic or polymer.Moreover, in shallower waters less expensive beads with a lowerisostatic strength may be used.

The insulation material 10 should include as large a quantity of themicro beads 14 as possible to facilitate effective thermal insulationwhile maintaining the brittleness of the insulation material belowmaximum acceptable levels. Thus, the insulation material 10 shouldinclude about 50-95% by volume of the matrix 12 and about 5-50% byvolume of the micro beads 14. Preferably, the insulation material 10should include about 65-95% by volume of the matrix 12 and about 5-35%by volume of the micro beads 14. More preferably, the insulationmaterial comprises about 75-85% by volume of the matrix 12 and about15-25% by volume of the micro beads 14. In one embodiment of theinvention, an acceptable insulation material 10 was achieved by mixing80% by volume of the matrix 12 with 20% by volume of the micro beads 14.It should be noted that micro beads 14 of two or more mean diameters maybe combined in order to achieve a larger concentration of the microbeads in the insulation material 10.

In accordance with the present invention, an exemplary insulationmaterial 10 may be obtained by mixing the following constituentsubstances in any order:

4 parts by volume of Silastic® E RTV silicone rubber; and

1 part by volume of Scotchlite™ H50/10,000 EPX Floated Series GlassBubbles.

Listed below are the relevant thermal and mechanical properties of thisinsulation material 10. All of these properties are within acceptablelimits for the intended applications of the present invention.

Property Value Hardness 45-55 Shore A Tensile Elongation up to 100%Thermal Conductivity 0.08 BTU/(hr · ft · ° F.) Density 0.95 to 1.10 g/cc

The insulation material 10 of the present invention can be used tothermally insulate any object from a surrounding fluid. In accordancewith one embodiment of the invention, the insulation material 10 is usedto insulate undersea pipes and wellhead equipment from seawater.

Referring to FIG. 2, for example, the insulation material 10 is shownapplied to certain portions of a subsea christmas tree 16. The subseachristmas tree with which the present invention may be used can be ofany known type of subsea christmas tree, including the so-calledhorizontal and conventional christmas trees. Such trees typicallyinclude an axial production bore 28 in communication with the well bore,a production outlet 30 connected to the production bore, one or moreproduction valves 32 for controlling flow through the production outlet30, a choke 20 connected to the production outlet 30 via a flow loop 24,an annulus outlet 34 connected to the tubing annulus surrounding theproduction tubing (not shown), one or more annulus valves 36 forcontrolling flow through the annulus outlet 34, and a production flowloop 26 for connecting the production outlet with an undersea pipe (notshown).

Ideally, the insulation material 10 is applied to those portions of thechristmas tree 16 which are most exposed to the surrounding seawater andthrough which the produced fluids will flow. For example, in FIG. 2 theinsulation material 10 is shown applied to the production valve block 18which houses one or more of the production valves 32, the choke 20, theannulus valve block 22 which houses one or more of the annulus valves36, and the flow loops 24 and 26. Of course, the insulation material 10may be applied to additional or fewer components of the subsea christmastree 16 as desired or required under particular circumstances.

The thickness of the insulation material 10 in the direction of heattransfer is preferably between about 0.5″ and 5″, and more preferablybetween about 2″ and 4″. However, the thickness of the insulationmaterial 10 may vary depending on the environment and the geometry ofthe surface to be insulated.

The insulation material 10 can be installed using a variety of methods.In the preferred method, a form or mold is constructed around the objectto be insulated. The material is then cast between the object and themold and allowed to cure. Once the material has cured, the mold isremoved. Alternatively, the insulation material can be pre-cast intosections which are shaped to complement the object to be insulated. Oncethe pre-cast sections have cured, they may be secured to the objectusing adhesives, mechanical fasteners, or any other suitable means. Theinsulation material can also be sprayed onto the object using a spraynozzle or similar device.

In accordance with an alternative embodiment of the invention, the microbeads 14 can be omitted from the insulation material 10. Although thethermal conductivity and density of this embodiment are inferior to thepreferred embodiment, this alternative embodiment exhibits superiorflexibility characteristics which may be suitable for certainapplications.

In accordance with another embodiment of the invention, the insulationmaterial comprises a base layer and an outer coating overlaying the baselayer. The base layer is preferably the insulation material 10 describedabove. The outer coating preferably exhibits a higher hardness anddensity than the insulation material 10, thus providing a protectivelayer for the base layer.

It should be recognized that, while the present invention has beendescribed in relation to the preferred embodiments thereof, thoseskilled in the art may develop a wide variation of structural andoperational details without departing from the principles of theinvention. Therefore, the appended claims are to be construed to coverall equivalents falling within the true scope and spirit of theinvention.

What is claimed is:
 1. A subsea christmas tree comprising: a productionbore; a production outlet connected to the production bore; a flow loopin communication with the production outlet; and a thermal insulationmaterial surrounding at least a portion of the flow loop; said thermalinsulation material comprising a silicone matrix and a plurality ofnon-metallic beads which are suspended directly in said matrix.
 2. Thesubsea christmas tree of claim 1, wherein said matrix comprises anaddition cured silicone material.
 3. The subsea christmas tree of claim1, wherein said matrix comprises a platinum cured, addition curedsilicone material.
 4. The subsea christmas tree of claim 1, wherein saidbeads comprise hollow glass beads.
 5. The subsea christmas tree of claim4, wherein said beads comprise a mean diameter of loss than about 60microns and an isostatic strength of at least about 10,000 psi.
 6. Thesubsea christmas tree of claim 4, wherein said beads comprise an epoxysilane surface treatment.